Television system



July 21, 1936. H, p PRATT l 2,048,517

TELEVISION SYSTEM Filed Aug. 5, 1955 i Patented July 21, 1936 UNITED STATES PATENT OFFICE 2,048,517 TELEVISION SYSTEM Harry P. Pratt, Chicago, lll.

Application August 5, 1935, Serial No. 34,697

9 Claims. v(01.178-6) The present invention relates in general to television systems and moreparticularly to providing a novel form of receiving device.

One of the objects of my invention is to provide a novel method of securing variable light control at the receiving end.

Another object is to provide a method by which the intensity of light can be read'ily controlled in response to impulses received from the transformer.

Another object is to provide a novel method of selecting the color of the' light desired and controlling it.

Still another object is to provide means for moving a light over a surface so as to produce an image.

There are other objects of my invention, which together with the foregoing will be described in the detailed specification that is to follow, taken in conjunction with the accompanying drawing.

Briefly, I provide an evacuated container having a cathode therein with means for concentrating the cathode beam and controlling its intensity. The cathode beam is directed upon a crystal which may or may not be in the form of a prism. Various types of crystals may be employed such as the piezo-electric crystal, or any other form of crystal such as one manufactured from quartz. The intensity of the electron emission from the cathode is controlled by a grid.

This application is a continuation in part of my application, Serial No. 628,962.

In the drawing:

Fig. 1 is a diagrammatic view of an embodiment of my invention suitable forl television work.

Fig. 2 is a fragmentary showing of a modication thereof showing means for moving the light beam.

Fig. 3 is a cross section of Fig. 2 taken along the line 3-3 looking in the direction of the arrows.

Referring noW to the drawing:

The reference character 4 represents a transformer of the usual type having a primary 5 which may be connected through the usual instrumentalities to a radio receiving circuit carrying the light impulses. The secondary winding B of the transformer 4 has one terminal connected to a grid or control electrode 1 in an evacuated container 8 which may be constructed of glass or other suitable material. The evacuated chamber 8 has a cathode 9 mounted therein surrounded by a reflecting electrode I0 having somewhat the shape of a parabolic reflector, and is adapted to focus the cathode beam upon an opening in a tubular anode II which is supported by an insulating support I2, which may be of mica or other suitable material. The filament 9 of the tube is connected through a variable resistor I3 to la battery I4 so that the amount of electrical en- .5 ergy flowing through the cathode can be controlled. One terminal of the secondary transformer 4 is connected to the iilament. The refleeting electrode I0 may be constructed, of any 'suitable material and is connected through a 10 biasing 'battery' I5 to the filament. The tubular anode II is also connected through a battery I8 to the cathode 9. whereby a potential is created between the cathode and anode. A crystal I'I of quartz; or other suitable material is positioned 15 within the tube in front of the tubular anode II and is suitably mounted in place so that the electron beam passing through the tubular anode will strike the crystal I'I. The crystal Il may be in the form of a prism if desired. I have found 20 a quartz crystal to be quite satisfactory. A screen I8 is suitably mounted in the end of the tube. Of course, the screen I8 may be mounted without the tube at some convenient point, if desired.

The tube of Fig. 1 is designedfor translating 25 y electrode I0 serving to concentrate the beam upon 35 the opening in the tubular anode. As the grid 'I is interposed between th'e cathode and the anode, the potential obtained from the space charge .will inhibit the flow of electrons toward the anode I I. However, in response to the incoming signal, 4o the space charge upon the gird 'I changes in accordance with the intensity of the impulse, thereby producing a change in the number of electrons forming the beam, extending through the tubular anode II. The electron stream strikes the 45 crystal Il and by the action of this crystal, a light ray is produced, having an intensity which varies in accordance with the intensity of an electron beam. If the crystal I1 is constructed in the form of a prism, the light emitted therefrom and 50 reflecting upon the screen I8 will be broken up into various colors so that the full spectrum will be obtained. However, by varying the frequency of the incoming signal, any one of the light colors of the spectrum can be selected so that one color 55 is emitted in response to the activation o! the crystal by the cathodebeam. This selection is deter. mined by the frequency oi' the incming ilnal superimposed upon the beam. Obviously. of course, the screen Il might be mounted outside the tube and a series of lenses interposed therebetween, i! it is desired to concentrate the light beam.

Should this type o! device be'used in a television receiving system, a light of "Hint intend' ty emittedbythe crystal I'Icanbepalledthrough the usual scanning device to build up a picture in any desired manner.

In Pigs. 2 and 3, I have shown a modincation ot my invention in which a scanning device is not necessary even when this type ot tube is used with present day television systems. This result is accomplished by mounting a pair ot4 deilecting plates Il and 20 within the tube between the anode l I and the crystal 2l. In this instance,

I have shown the crystal 2i in 2 units so that'A white light only is emitted therefrom. Obviously.

ot course, a prismatic type of crystal could be employed so as to secure color asshown in Fis. 1.

In addition to the deilecting plates Il and Il a pair of coils 22 and 23 mounted either within or without the tube can be employed. These deilecting coils are connected together and thence to a low frequency oscillator which generates an oscillating current in the neighborhood say from 30 to 60 cycles. The dedecting plates are connected to another oscillator which generates an oscillating current of high frequency. The deecting plates will dedect the cathode beam after it passes through the tubular anode in an up and down direction while the coils Il serve to `cause the beam to move over an area. 'Ihe cathode beam is thus caused to move over the area of the crystal 2|. The excitation oi' the crystal converts the cathode stream into light rays of an 'intensity proportional to the incoming signal.

'Ihis light beam however, is caused to cover the area on the screen il and reproduce the picture y thereon by .reason of the .deilections occurring in the cathode beam.

The crystals i1 and 2| act as translating devices for converting'the cathode .beams into light beams. It is relatively diilicult to cause a light beam to traverse an area except mechanically, whereas the electronv beam. or cathode stream may be deiiected readily magnetically orelectrostatically.` Ot course, in the modiiication shown in Figs. 2 and 3, the screen I8 may obviously be mounted outside o! the tube.

whue r have illustrated and described certain speciiic embodiments of my invention, I am aware it may be variously changed and modiiied without departing from the spirit and scope thereof as set forth in .the appended claims.

I claim:

1. In an electronic device. a cathode, an anode, a control electrode interposed between said cathode and anode, a crystal mountedv on the other side ot said anode, and a screen mounted Withinl said device beyond said crystal.

3. In a thermionic device, a cathode at one end oi' said device and a tubular anode adapted to cooperate to form an electron stream and a crystal mounted in the path of said stream and ascreen mounted at the other end of said device.

3. In a thermionic device, a cathode at one end of said device anda tubular anode adapted to cooperate to form an electron stream and aprismatic crystal mounted in the path or saidstream and a screen mounted at the other end of said y device.

4. In a thermionic device, a cathode at one end of said device and a tubular anode, adapted to cooperate to forman electron stream and a piezo electric crystal mounted in the path 4of said stream and a screen mounted at the other end of said device.y

5. In a thermionic device, aA cathode at one means for creating an electrical eld between said anode and crystal.

'1. A cathode ray tube having. a cathode, an anode and a screen, and a crystal mounted between said anode and screen.

8. A cathode ray tube having a cathode, an

, anode and a screen. and a quartz crystal mounted between said anode and screen.

9. In a television system, an electron tube haus-1 y ing a cathode, an anode, control electrode, and a screen, means for scanning the area of the screen, and a crystal mounted in the path of the 'electron beam between the screen and said anode.

HARRY P. PRATI'. 

